This invention relates to the art of incinerators for burning combustible materials contaminated to some extent by radioactivity. More particularly, the invention is directed toward the measurement of radioactive residuals in an automated incinerator system burning various kinds of combustible radioactively contaminated materials.
The manufacture of nuclear fuel requires personnel and equipment to come into contact to a limited extent with fissile and fertile radioactive substances such as uranium dioxide. Certain materials such as cloth, paper, rubber or plastic retain an amount of these radioactive substances and are deemed contaminated. Over time, such contaminated materials accumulate and are desirably disposed. Insofar as these materials are combustible, they can be burned in an incinerator. This reduces the quantity of material, diminishes the overall waste disposal problem to more manageable proportions, limits the consumption of financial resources, and generally provides a more satisfactory solution than the burial of the material.
One concern, however, is that the residual radioactive ash will accumulate in the incinerator and become critical. Most important, the mechanical elements moving the ashes out of the incinerator may, upon retracting, retain an excessive amount of radioactive ash in the incinerator. Some warning or detector indication of the amount of retained radioactive ash in the incinerator is required. In fact, to cover the entire inner surface of the incinerator, where ash is likely to accumulate, several detectors may be required.
Radiation detectors, however, are not likely to survive within the incinerator. Outside the incinerator on the other hand, the detectors are ineffective for detecting radioactive accumulations within because of the shielding effect of the massive walls of the incinerator.
Accordingly, it is an object of the instant invention to provide an arrangement that can detect radioactive accumulations at several locations within the incinerator containment.
Further, it is an object to construct an incinerator in a manner which enables radiation detectors to "see" into the incinerator and detect radioactive accumulations within.
It is an object to create an automated incinerator system capable of providing status indications of its own operability, specifically with regard to the level of radioactive accumulations within the incinerator.
Accordingly, an incinerator is provided with low density "windows" of refractory material, which windows protect radioactivity detectors from the heat within the incinerator while still permitting the detectors to detect the level of radioactivity accumulations in the incinerator behind the window.